It has been observed that light deprivation over a 20-minute period brings about highly significant decreases in the rate of function of both the parotid and submaxillary glands in the human. These observations will be extended to investigate the time course of secretion from these glands at very narrow intervals of time. Studies are also planned in persons who have been blind for varying periods of time. Secretory IgA studies in saliva will be enlarged to include a group of patients receiving irradiation for head and neck malignancy. As flow is depressed by progressive irradiation, IgA secretory patterns will be studied. These data will be compared to similar results from healthy patients not undergoing irradiation. Long-term fluoride studies will be completed to determine the minimal level of fluoride required in saliva to reduce enamel solubility. Oral fluoride administration studies will continue in efforts to maintain elevated salivary fluoride levels over extended time periods.